This invention relates to a fluidized bed reactor and a method for operating same, and, more particularly, to such a reactor and method in which the entrained particulate material from the bed is separated from the entraining mixture of gaseous products of combustion products and air and reinjected back into the bed at multiple points.
Fluidized bed reactors, in the form of combustors, boilers, steam generators and the like, have long been recognized as an attractive and effective means of generating heat. In these arrangements, air is passed through a bed of particulate material which normally consists of a mixture of reactive and/or inert material and a particle fossil fuel, such as coal, to fluidize the bed and to promote the combustion of the fuel. The fluidized bed offers an attractive combination of high heat release, improved heat transfer to surface within the bed, and compact size.
During the operation of a fluidized bed, the fluidizing air mixes with the gaseous products of combustion and the resulting mixture entrains, or elutriates, a significant portion of the relatively fine particulate material in a bed, which is carried out of the furnace and not utilized. Some known arrangements of fluidized beds incorporate a cyclone separator, or the like, to separate the entrained solid particulate material from the mixture of air and gaseous products of combustion, and the separated material is then reinjected back into the bed. However, the reinjection point is usually at one location either above the surface of the bed or below the surface of the bed which results in less than uniform distribution of the particulate material in the bed, and thus compromises the total fuel burn-up efficiency. Also, these reinjection systems normally employ a means of pneumatic transport which are fairly complex and require a relatively high volume of air to achieve the reinjection process. Further, these type systems suffer from a relatively high power consumption and a relatively high degree of material clogging in the separator hoppers.